Police were originally responding to an unrelated call when they approached Crutcher’s vehicle, which had been stalled in the middle of the street. Shortly after the officers arrived, one officer deployed his taser on Crutcher who stood by his car. Moments later, Officer Betty Shelby, who is white, fatally shot Crutcher, who was black and unarmed, while he had his hands raised in the air, according to this graphic video footage released on Monday. In one video that was captured by an overhead helicopter, Crutcher is seen standing by his car while a police officer is overheard describing him as a “bad dude.”

“That big ‘bad dude’ ― his life mattered,” Crutcher’s twin sister Tiffany Crutcher told reporters on Monday, according to Tulsa World. She went on to demand an end to police brutality. “The chain breaks here. We’re going to stop it right here in Tulsa, Oklahoma. This is bigger than us right here. We’re going to stop it right here.”

Tiffany, who just celebrated her 40th birthday with her brother, mentioned a recent text message she received from Terence that she said read, “I’m going to show you. I’m going to make you all proud.”

She expressed her grievance over his loss and how Terence will never get that chance, “because of the negligence and the incompetency and the insensitivity, and because he was a big, ‘bad dude,’” Tiffany said. “And so we’re demanding today, immediately, that charges are pressed against this officer that was incompetent, that took my brother’s life.”

Dozens of Crutcher’s family members gathered for a news conference on Monday alongside their attorneys including, Benjamin Crump who has represented the families of other police-shooting victims. Police claim that Crutcher failed to follow the officers’ commands, but his family lawyers say that the videos show otherwise, and they plan to send a letter to U.S. Attorney General Loretta Lynch to ensure that a proper and thorough federal investigation takes place.

“This presented itself, to our thinking as lawyers, as a case involving someone in distress, someone needing help from either a mental or a medical condition — perhaps intoxicated, but in a condition needing assistance of the police,” the family’s attorney David Riggs said at the conference. “But the police seemed to have approached it as someone who was a threat to the community.”

Other family members and lawyers echoed this sentiment at the conference.

“When Terence was shot, he laid on the ground bleeding out without any assistance,” Dario Solomon-Simmons, an attorney for the family and longtime family friend, said at the conference. “Terence died on that street by himself in his own blood, without any help.”

“This video is extremely disturbing,” he added. “Without a doubt we believe this was an unjustified shooting that should not have happened.”

The anger around Crutcher’s death has been felt from many on social media who have poured out their grievances online over the police killing of yet another unarmed black man with the trending hashtag #TerenceCrutcher. However, as the mourning continues, Crutcher’s sister has asked that people remain peaceful as they demonstrate their anger over his death.

“Just know that our voices will be heard,” she said. “The video will speak for itself. Let’s protest. Let’s do what we have to do, but let’s just make sure that we do it peacefully, to respect the culture of (the Crutcher family).”